Waste water: composition, analysis, purification. Wastewater treatment plants. Wastewater treatment: methods and modern techniques Wastewater treatment
Sewerage wastewater treatment This is a set of required activities. Its implementation is regulated by the current legislation and which is necessary both for the purpose of protecting the environment and for the renewal of water resources. Modern purification technologies using various methods in their nature make it possible to ensure maximum purity of the liquid returned to nature.
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What is meant by waste water?
Sewer wastewater is called:
- all liquid waste from human life and activities, the so-called domestic waste;
- industrial effluents, water used directly in production, as well as for cooling systems;
- atmospheric precipitation that enters the sewer through the storm sewer system.
According to the types of pollution, wastes are classified as follows:
- Minerals containing:
- salt;
- sand;
- clay, etc.
- chemical organics;
- polymers.
As a rule, sewage drains are a combination of all types of pollution, which makes it necessary to carry out their multi-stage purification.
The cost of sewerage wastewater treatment
| Name of service | Price |
| Maintenance of heat substations (independent scheme) | from 6 000 rub/month |
| Maintenance of heat substations (dependent scheme) | from 10 000 rub/month |
| Maintenance of UUTE | from 3 000 rub/month |
| Installation UUTE | from 250 000 rub |
| Hydraulic tests (pressurization) | from 7 000 rub |
| Chemical flushing of the heat exchanger | from 8 000 rub |
What methods are used to clean sewage?
A variety of contaminants makes it necessary to treat sewage wastewater according to a combined scheme using the following methods.
- Mechanical.
It is used to remove large particles and insoluble residues and serves as a preparatory step for subsequent biological cleaning.
Sorting of this group of waste can be done in the following ways:
- straining;
- filtration;
- upholding;
- centrifugal filtration.
The combination of these methods used in practice can significantly increase the efficiency of mechanical cleaning.
This method is used, as a rule, for the treatment of industrial effluents and consists in the addition of chemical reagents that contribute to the transformation of soluble components into insoluble ones for their subsequent removal by a mechanical method.
The action of reagents can also be directed to such reactions as:
- neutralization;
- oxidation;
- recovery.
In practice, due to its high cost, the chemical method in its pure form is used extremely rarely.
Being a combination of the use of physical and chemical properties of liquids and trace elements, this group of methods is considered the most effective for treating a wide range of wastewater, including industrial waste.
There are the following cleaning methods:
- electrochemical;
- coagulation;
- sorption;
- ion exchange;
- extraction, etc.
It should be noted that the complex application of the physicochemical method allows not only to obtain an almost pure liquid at the outlet, but also to fully automate the entire process.
These purification methods are based on special bacteria capable of processing human waste products with a degree of purity of the liquid at the outlet up to 95%.
By type of bacteria can be:
- aerobic, which require air to live;
- anaerobic, living without access to oxygen.
The use of bacteria is considered the most promising direction in the purification of polluted wastewater, but this method is not suitable for processing wastewater from industrial enterprises.
However, in the residential sector and in the urban economy, this method is used quite widely.
It is used in the case when liquid purification is not possible, as well as for liquid waste immediately after the relevant processes have been carried out. The essence of the method is to spray a contaminated liquid over a burning fuel torch.
Calculate the cost of sewage treatment for you
In order to select the optimal treatment method, sewage effluents in a particular area are subjected to a thorough analysis to determine their composition, on the basis of which the most effective combination of methods is developed.
The purification processes themselves take place at specialized stations, which are a complex system of tanks, sedimentation tanks, filtration modules, etc. The composition of the equipment is also determined by the composition of specific waste.
Thus, sewerage wastewater treatment is a process that involves the use of a variety of methods and technologies. The general reduction of water resources increases the importance of this area, and state regulation is an additional incentive for improving technologies in this area.
The chemical method of wastewater treatment is usually used in industrial production, where, as a result of activities, water is polluted with various substances. In order to remove various impurities from polluted water, special reagents are added to it, which help to form sparingly soluble substances that precipitate. The chemical method of purification also involves the disinfection of already purified water using chlorine-containing reagents that destroy pathogens.
Mechanical wastewater treatment
Mechanical wastewater treatment helps to remove large debris and particles of mineral origin, which are in the effluent in an undissolved suspended state. During mechanical treatment, wastewater passes through sand traps, grates and special filters, then it settles in a sump, where it is partially filtered and clarified. This method is used immediately before biological treatment.
Biological sewage treatment
Biological treatment is designed to free wastewater from organic compounds dissolved in it. This process involves special groups of microorganisms: aerobes, which develop only in the presence of oxygen in the wastewater, and anaerobes, which require oxygen deficiency. Accordingly, cleaning can be aerobic and anaerobic. Modern wastewater treatment plants use a combination of anaerobic and aerobic treatment, which gives excellent results.
Aerobic purification takes place in aerotanks, in septic tanks with a biofilter, in filtration and absorption fields, in filter wells with natural and forced air supply. Forced air supply is created in treatment plants using compressors. In all other cases, oxygen comes from the surrounding air. This chemical element is the main one in the process of vital activity of aerobic bacteria. In the presence of oxygen, aerobes begin to actively multiply and feed on organic pollutants, resulting in intensive purification of wastewater. In parallel, the formation of activated sludge in the treated water is observed. Activated sludge is a very useful substance, as it mixes with sewage and causes the oxidation of dangerous organic compounds, turning them into simple and harmless components. As a result, the water is freed from bacterial contamination, becomes transparent, and loses the unpleasant smell of sewage.
The advantage of aerobic treatment is the almost complete purification of wastewater from organic matter. Anaerobic purification occurs without air access. For this, special closed tanks are made, where oxygen deficiency is created.
Such conditions are favorable for anaerobic bacteria, which are involved in the fermentation and decomposition of organic matter into water, methane, carbon dioxide and other simple compounds. Anaerobic treatment takes place in septic tanks, metatanks and special two-tier settling tanks.
- Heating pipes with a heating cable and other methods of insulation
Wastewater generated in the course of human life, entering water bodies, becomes one of the most serious sources of pollution that negatively affects human health. To reduce the pollution of water bodies, a set of measures is applied to cleaningWastewater- removal of contaminants. Drains, depending on their origin, are divided into the following types:
- Household or household-fecal, which include receipts from residential development and public buildings;
- Production - formed in technological processes and removed from the territories of industrial enterprises;
- Rain, collected during rainfall, snowmelt and washing of territories.
Households are contaminated with all sorts of organic impurities, including food debris, and carry a huge amount of bacteria, both neutral and pathogenic. The main task of processing such wastewater is the extraction of large and small inclusions, the oxidation of organic matter contained in them, in order to reduce the burden on the environment and disinfection.
Industrial effluents, also depending on the nature of their formation, may contain a variety of organic ingredients, such as dairy effluent, mineral inclusions and other compounds harmful to life. Liquid waste generated at metalworking enterprises contains metals, including heavy ones, which, if ingested, can have a negative impact on human health.
Rain runoffs wash away organic impurities, suspended particles (sand, clay, etc.) and oil products from the territories.
Effluent of various origins contains a variety of pollutants. The discharge of rainwater into water bodies without treatment leads to serious pollution, adversely affects human health, can accumulate in the inhabitants (fish) and, accordingly, enter the body with food.
For cleaning, various methods are used, which depend on the nature of the formation of liquids, their composition and quantity. Let's consider the methods of treatment of household water, because. they make up the largest part of stocks.
Domestic wastewater treatment methods
Wastewater entering the treatment plant goes through several stages of processing:
- mechanical;
- biological;
- disinfection.
For the mechanical stage, the following equipment is used: gratings, sand traps, sedimentation tanks, filters. The first structure that drains fall on is gratings. They are a set of rods installed vertically or with an inclination on which large inclusions are retained. The recommended clearance between the bars is 16 mm. The retained debris is removed from the screens manually (for small stations) or with a mechanical rake. The collected garbage is collected in a special container, then taken to a landfill.
The following equipment is used for the mechanical stage: gratings, sand traps, sedimentation tanks, filters The next stage is settling in sand traps, which are rectangular or round in terms of structures. When entering the sand trap, the speed of movement decreases, and heavy ingredients, mainly of mineral origin (sand), settle. These particles carry all pollutants. Sand settles to the bottom of the sand trap, is moved by scrapers or washed off into the lower part of the pit, then removed by pumps or water jets to the sand platform. After drying, the sand must be disinfected and can be used, including for planning work.
After preliminary treatment, water enters the primary settling tanks, which, depending on the direction of movement in them, are divided into horizontal, radial and vertical. The choice is determined by the performance of the structures. With low productivity, vertical ones can be used, with medium productivity - horizontal ones, for large stations radial ones are used. The principle of operation of settling tanks is the same - with a decrease in the speed of movement, impurities of various sizes are released. The speed of movement in settling facilities is determined by regulatory documents. Impurities settle to the bottom, then by scrapers, liquid jets or under the action of their own weight they move to the pits, then they are pumped for further processing. There are various methods of settling intensification, first of all, it is a reagent treatment, when chemicals are added that contribute to the coarsening of suspended particles. Larger particles settle faster. Another way is thin-layer settling, when a set of shelves is placed in the sump and the process goes faster by reducing the settling height.
Secondary clarifiers are related to mechanical cleaning designs, but are located after the biological treatment stage, which will be discussed in the next section. Secondary, as well as primary, are divided into horizontal, radial and vertical, but not suspended solids are released in them, but activated sludge, which is formed in aerotanks or biofilters.
The next stage is settling in sand traps, which are rectangular or round in terms of structures. Filtration is used for deep purification from contaminants. This process completes the technological scheme and is used in cases of stringent requirements for the quality of runoff discharged into water bodies. Post-treatment is carried out on filters of different designs, the choice of which depends on the performance of facilities and pollution. Filtration is carried out through various media, mainly natural materials of various sizes, the most popular of which is quartz sand.
Biological treatment
Settled effluents enter aerotanks - biological oxidation plants. In aeration tanks, water is mixed with activated sludge - flaky compounds of bacteria, air is also supplied here in the form of small bubbles. Bacteria in the presence of air actively absorb organic ingredients, they are oxidized and the amount of activated sludge increases. The mixture flows into the secondary settling tank, where the sludge settles, then part of the sludge is removed for processing, and part is returned to the aeration tank. With low productivity, instead of aerotanks, biofilters are used - tower-type structures filled with a special load and ventilated from below. Bacteria settle on the load. The liquid, moving from top to bottom through the load, comes into contact with bacteria in the presence of air and is intensively cleaned.
Purified liquids contain a large number of bacteria, including pathogens, so they must be decontaminated before being discharged into a reservoir. For disinfection are used:
- sanitation with chlorine-containing reagents;
- ozonation;
- ultraviolet irradiation.
Each method has its own advantages and disadvantages. Chlorination involves the use of chlorine - a toxic substance, so working with it requires special care. The liquid after chlorination must be kept for at least half an hour to remove chlorine compounds. For this, contact tanks are used.
Purified liquids contain a large number of bacteria, including pathogens, so they must be decontaminated before being discharged into a reservoir. Such tanks, with high productivity, occupy significant areas. Ozonation is an expensive energy-intensive procedure and is carried out in sealed structures. UV disinfection is limited in performance.
In the process of processing household wastewater, primary sludge is released in primary settling tanks, after aerotanks, activated sludge is released in secondary settling tanks.
Recycling and subsequent disposal of the resulting sludge is one of the most serious tasks of sewage. The complexity of the task is determined by their large volume and properties. As a rule, sediments are hard-to-filter suspensions of organic origin. Their volume, depending on the composition and technological scheme, is 0.5 - 10% of the flow rate supplied to the treatment facilities. Their humidity is 90 - 99%, most of the moisture is in a bound state. The bacteria and helminths contained in them require serious disinfection before further use.
Recycling and subsequent disposal of the resulting sludge is one of the most serious tasks of sewage. The main tasks are the reduction of humidity, stabilization, disinfection.
To transfer the main part of organic matter into a mineral form, methane digestion and aerobic stabilization are used. Methane fermentation is carried out in digesters, where, under the action of high temperature, the sludge is mineralized, and gas is released - methane, which can also be used at treatment facilities for their own needs. The difficulty lies in the contamination of the gas with impurities. During fermentation, in addition to mineralization, the issue of disinfection is solved.
Aerobic stabilization is used to mineralize the active or. The process is an active aeration of sludge in structures similar to aeration tanks. The next step in the processing of sludge is their dehydration. For dehydration, natural methods are used (drying on sludge beds) and mechanical methods (on belt or chamber filter presses, centrifuges, vacuum filters). Before dehydration, to transfer moisture from a bound form to a free one, it is treated with reagents or flocculants. Dehydrated sludge with a moisture content of 70 - 80% (depending on the method of dehydration) is fed for further processing - disinfection - mainly by thermal methods.
After disinfection, the sediment is suitable for use as a valuable fertilizer.
Wastewater treatment plant
The process of urbanization and, in particular, the expansion of communal services complicates the tasks of urban service organizations. The fight against sewage pollution is especially important in this regard, since the waste from the consumption of household fluids has a direct impact on the hydrological system of the area. In this regard, more effective means of minimizing the negative processes of environmental impact are being developed. Today, wastewater treatment is organized taking into account several factors for the elimination of harmful microorganisms. The main method of water purification is still the arrangement of mechanical filtering stations, but more and more complex installations are appearing that also perform high-quality biological water treatment.
Features of modern wastewater treatment
Engineering equipment is developing in general directions that focus on improving ergonomics and reliability. Therefore, modern sewage drains are multifunctional, efficient and easy to manage. Both industrial and domestic wastewater filtration systems are equipped with control panels with a wide range of settings.
In addition, the developers of sewer and septic systems projects strive to rationalize communication networks as much as possible, optimizing energy resources as well. In other words, wastewater treatment at some sites can also be connected to complex engineering management systems for a home or enterprise. And this is not to mention the increase in the basic operational capabilities of cleaning equipment, which is achieved through the use of high-tech
mechanical cleaning
The whole cleaning process is divided into several stages, which have significant technological differences. The stage of mechanical filtration is primary and at the same time multi-stage. The simplest mechanism for such cleaning can be observed on the streets in the form of metal, concrete or plastic gratings that trap debris, leaves, stones and other large elements. In the future, wastewater can be sent through the sewer channel to special centrifuges and hydrocyclones. Also, a special strainer is used to trap microscopic particles - in essence, this is a filtration cleaning station. The drain, thanks to such equipment, can be cleaned of elements up to 0.25 mm in size. Together, the cleaning steps at this point can eliminate about 80% of foreign bodies in the waste fluid.
Biological treatment
Means of this kind of cleaning are usually used as a continuation of mechanical filtration. It can be said that the basic purification by strainers prepares the liquid for deeper processing by biological stations. However, both methods work on different principles. That is, it is wrong to assume that mechanical filtration traps large particles, and biological installations - small ones. The second option focuses on the environmental neutralization of water, which does not cause chemical harm during maintenance and after its release into water bodies. To date, the biological treatment of wastewater, the main goal is the elimination of organic matter or its processing. As a result, the composition of the liquid medium retains only dissolved nitrates and oxygen. In practice, such cleaning is implemented in two ways - natural or artificial. In the first case, wastewater is dispersed into and into artificial purification is carried out in special aeration tanks that release environmentally friendly water into reservoirs.
Chemical and thermal cleaning methods
From the point of view of eliminating the negative processes of decomposition in the sewage environment, one of the most effective methods is chemical reagent. As a rule, this group of methods is based on redox reactions, which essentially cancel some reactions, replacing them with others that are less environmentally hazardous. But the most effective method of combating pollution in wastewater is thermal exposure. This method is carried out using furnace installations and burners in which the liquid is burned. Wastewater treatment by the fire method is also practiced without the use of furnace structures. Technologically, this method involves spraying a liquid in a finely dispersed state into a special torch formed during the combustion of gaseous fuel. As a result, water evaporates, which eliminates harmful compounds.
Sludge disposal
New technologies, which ensure the complete elimination of decomposition products, are not yet used at all treatment facilities. Moreover, such a principle does not always justify itself economically. Therefore, traditional cleaning channels are still common, the operation of which leaves sediments. New technologies in such recycling processes manifest themselves at the final stage of waste disposal. In particular, digesters are used. These are massive reinforced concrete tanks in which biogas is formed by fermentation. As a result, methane fuel is formed, which can later be used in boiler houses instead of traditional fuel. Also, complex wastewater treatment with sludge elimination involves the use of mechanical dehydration methods using special devices - centrifuges, belt or chamber pressing plants. In the future, the products of such processing, depending on the chemical composition, can be used in agriculture as a fertilizer.
Conclusion
At this stage in the development of sewer systems, many manufacturers are solving the problem of a complete transition to one of the cleaning methods. This is due to the fact that the technical organization of several stages of processing contaminated liquid is expensive and requires the connection of large resources in the maintenance process. As an alternative, a biological wastewater treatment plant is considered, which also provides for the functions of mechanical processing, but only as auxiliary stages. However, this option cannot be called universal, since biological aerotanks lose in terms of the efficiency of removing harmful particles to the same thermal cleaning. Therefore, it is still advisable to approach the solution of the problem of wastewater treatment through the development of projects that take into account the individual conditions and requirements of the treatment equipment.
Plumbing is an integral part of modern comfort, and where there is water supply, there must also be drainage. But what to do with the accumulated waste? Now there are many options for solving this problem, ranging from primitive recycling to complete purification of the contaminated fraction from process water. This article discusses the most common methods of wastewater treatment, the principle of their operation, the main pros and cons of such systems.
Wastewater treatment methods
First you need to understand what is wastewater? This category includes any drains that contain any impurities and contaminants. These include:
- Household sewerage of the residential sector. It contains mainly waste products, biological waste of animal origin, such as fat and food particles. Wastewater treatment technology can be done locally or globally;
- Industrial effluents contain production waste, chemical elements, polymers or petroleum products. The processing of such contaminants differs from cleaning domestic sewers, this process is more complex and includes a set of activities with several levels. Such installations are able not only to process wastewater, but also to provide the enterprise with water for production needs.
Thus, based on the type of sewage, it is possible to determine the type of treatment plant that will be most appropriate to achieve the desired result and level of treatment.
Wastewater treatment methods can be classified into three types:
- Mechanical methods of wastewater treatment. As a rule, this stage is considered preparatory, since this is the most primitive method in which there is no other than physical impact on pollution from large fragments. Mechanical wastewater treatment is carried out in several ways:
- Straining. At this stage, the drains are passed through a steel or plastic grate that holds large elements and fibers. Most often, such a mechanism is equipped with an electric drive, it rotates the grid during the water supply, and at the top point all contaminants are removed for disposal;
- Settling. The settling mechanism is based on the physical property of the material to settle on the bottom of the tank. Since water is lighter than the main types of pollution, all elements sink down and accumulate in the water column. After precipitation, contaminants are removed from the sump by emptying it or draining through the bottom of the channel;
- Filtration is carried out using a catching grid with a fine mesh. This method is justified in cases where there are no large contaminants in the effluents or as an intermediate stage of treatment;
- Separation or centrifugation. One of the most modern types of separation of water from dirty drains. The principle of operation of this device is based on the movement of water in a spiral in a special drum, in the process of such rotation, large and suspended particles are separated from industrial water.
This method is one of the main methods of wastewater treatment.
- Chemical methods of wastewater treatment. This method is designed to separate substances dissolved in wastewater from the main mass by adding special reagents, which, when released into a polluted environment, react with the liquid and contribute to the precipitation of harmful substances. Chemical wastewater treatment, depending on the additives used, is divided into two subsections:
- Neutralization with acids and alkalis. At this stage, chemicals are added to the drains, which bring the liquid to the required value and weight of hydrogen. Most often this method is used in the textile and other industries;
- Oxidation using chemical reagents, which can be liquefied chlorine and its other derivatives. The main direction in the processing of such an installation is the treatment of wastewater with a high content of heavy metals.
- Physico-chemical methods of wastewater treatment. This is one of the most advanced methods of disposal of contaminated liquid, which includes several stages of separation and removal of finely dispersed and hardly soluble organic and non-organic elements. As well as the previous methods of processing wastewater, this process can be of several types:
- Coagulation is an action based on coarsening by sticking together small particles when reacting with added reagents. The most commonly used salts are ammonium, copper and iron. In domestic conditions, it is rarely used due to the high cost and large dimensions of the equipment;
- Flotation. In this case, a special installation is needed, into which sewage flows, and natural or chemically created flotation agents, such as oil or petroleum by-products, are added. In order for the cleaning process to be continuous, compressed air is supplied to the separated chamber under high pressure, which, passing through the drains, forms a foamy emulsion. Flotation forms oxygen bubbles that capture molecules from the total composition and lift it to the upper layers. The result is an aggregation of elements in a dense foam. This method is used in metal mining to separate useful ore from other minerals. Also, flotation is used in modern urban wastewater treatment plants;
- Sorption cleaning of household drains. The most advanced cleaning method, it uses large sorbents of natural or chemical origin. Contaminated effluents are mixed with porous material, and after settling into a sediment, the filter is removed from the tank, and the technical fluid can be reused. The level of purification with this method reaches a degree of 95%. The main disadvantage of sorption is the high cost of components and equipment;
- Simple and reverse osmosis. In such a device, domestic wastewater treatment occurs as a result of squeezing water through contaminated drains and a membrane, or the reverse process with the passage of dirty water through a filter element and the separation of waste molecules. The principle of operation in both directions is the same, it is based on the mechanical retention of particles that are larger than water molecules in a special grid. After the filter is filled, it must be removed and changed or cleaned.
All physical and chemical methods of wastewater treatment are mainly used on an industrial scale for large enterprises and factories. The production and household methods differ in the equipment used and the number of processes. But some units are also used in the private sector, for example, flotation or osmus.
- Biological method of sewage treatment. Most often, this method is used in the construction of treatment facilities for an individual dwelling with an autonomous communication system. Its principle of operation is based on the processing of contaminants by creating a nutrient medium for special bacteria intended for wastewater treatment. There are two types of microorganisms suitable for wastewater treatment:
- Anaerobic bacteria - live in a polluted airless sewer environment and feed on biological waste. Anaerobic wastewater treatment has a methane gas by-product, so the tank must be equipped with a gas vent. Another colony of bacteria is called useful sludge, as they live on sand particles contained in the aquatic environment;
- Aerobic bacteria, unlike the previous ones, need a constant supply of air, since they need oxygen for normal life. The waste tank must be equipped with a compressor unit and a supply of pipes for effluent enrichment.
Often, both options are used sequentially to achieve the desired result, then the level of sewage treatment can reach 98%. Such water cannot be used for food, but it is suitable for domestic needs, for example, for watering plants or cleaning. Often the aerobic scheme is used in conjunction with another oxygen method called flotation.
Note! Regardless of the chosen method of domestic wastewater treatment, its design and installation should be carried out by qualified workers, since it will be possible to independently calculate the required power only with a detailed study of all communication parameters.
Stages of wastewater treatment, stages and installation of an autonomous septic tank
Treatment of domestic wastewater in the enterprise and in the private sector are very different from each other. In individual housing, a combined treatment system is often used, which includes several stages of liquid treatment to the state of process water. The construction of such a structure begins with the calculation of power and location. As a rule, the septic tank is located at some distance from the residential building closer to the exit from the site. This is done so that during operation there are no problems with the removal of waste material and waste.
The next step will be digging a pit for the tanks. Many manufacturers make rigid plastic tanks with built-in baffles and compartments for overflow, filtration and recycling. Such a product is much more expensive than reinforced concrete rings, since its production is expensive, but has the advantage of ease of installation and maintenance, as well as space saving. Warranty for plastic containers for more than fifty years.
It is important to observe the dimensions of the pit so that it is 20-30 cm larger around the perimeter, this will facilitate installation and prevent the destruction of the walls of the pit.
Geotextiles are laid on the sand and gravel cushion, which will prevent the container from sagging under the influence of heavy weight. After ramming the base, the septic tank itself is mounted, it can be factory-made or made independently from reinforced concrete rings. If a plastic tank is used, then weighting must be placed on the bottom so that when precipitation occurs, the container does not float out.
The sewer pipe is connected along the top cover in such a way that there is an air gap between the accumulated drains and the incoming liquid. To prevent the entry of an unpleasant odor from the septic tank into the room, it is recommended to install a check valve that works only in one direction, regulating the flows.
Most often, the first stage of sewage water treatment is natural filtration from large fragments of non-biological origin. For this purpose, an overflow threshold with a sand trap is provided in the tank, which screens out elements unsuitable for processing from the bulk.
Anaerobic bacteria are located in the next compartment, which purify the liquid from large inclusions that are contained in the thickness of the drains. After processing the main pollution and turning them into carbon dioxide and methane, the bacteria partially die; in order to maintain the required number, it is necessary to periodically renew their population.
After overflow, the recycled water enters the aeration fields. Bacteria live here, feeding on biological waste when enriched with oxygen. Therefore, to ensure the process, it is necessary to continuously supply oxygen to the chamber; without it, all microorganisms will die.